Fabrication of a micro-scale, indium-tin-oxide thin film strain-sensor by pulsed laser deposition and focused ion beam machining

Abstract

Abstract A thin film strain-sensor having an active sensing area of 20 mm ×100 mm has been developed using a combination of pulsed laser deposition (PLD) and focused ion beam (FIB) machining to net shape. Sensors were made of indium-tin-oxide (ITO) thin films in the range 100–246 nm thick. Strain sensitivities of large-scale (smallest dimension=0.8 mm), small-scale (smallest dimension=0.25 mm) and FIB machined gages (smallest dimension=20 μm) are reported. Large-scale devices were deposited in a background oxygen pressure in the range 28–50 mTorr, while small-scale and FIB machined gages were deposited in 50 mTorr of oxygen, the largest achievable pressure in our system, which also yielded the largest strain sensitivities. Active strain-sensors were produced with gage factors ranging from −0.3 to −8.7 and showed a linear room temperature response with minimal hysteresis. The effects of imaging and machining with the FIB as well as the effects of an SiO 2 encapsulation layer on the electrical properties of the gages are reported.